Polymers

16 pages, 4247 KiB

Open AccessArticle

Analyzing the Potential of Laser Femtosecond Technology for the Mass Production of Cyclic Olefin Copolymer Microfluidic Devices for Biomedical Applications

by Irene Varela Leniz, Taieb Bakouche, Malen Astigarraga, Florent Husson, Ane Miren Zaldua, Laura Gemini, José Luis Vilas-Vilela and Leire Etxeberria

Polymers 2025, 17(9), 1289; https://doi.org/10.3390/polym17091289 - 7 May 2025

Viewed by 264

Abstract

Precision micromilling is currently widely used for the fabrication of injection mold inserts for the mass production of microfluidic devices. However, for complex devices with micrometer-scale and high density of structures, micromilling results in high production times and costs for production runs of [...] Read more.

Precision micromilling is currently widely used for the fabrication of injection mold inserts for the mass production of microfluidic devices. However, for complex devices with micrometer-scale and high density of structures, micromilling results in high production times and costs for production runs of hundreds or thousands of units. Femtosecond laser (fs-laser) technology has emerged as a promising solution for high-precision micromachining. This study analyzes the potential of fs-laser micromachining for the fabrication of injection mold inserts for the large-scale production of thermoplastic microfluidic devices. For the evaluation of technology, a reference design was defined. The parameters of the fs-laser process were optimized to achieve high resolution of the structures and optimal surface quality, aiming to minimize production times and costs while ensuring the quality of the final part. The microstructures were replicated in two different grades of COC (Cyclic Olefin Copolymer) by injection molding. The dimensional tolerance of the structures and the surface finish achieved both in the insert and the polymer parts were characterized by scanning electron microscopy (SEM) and confocal microscopy. The surface quality of the final parts and its suitability for microfluidic fabrication were also assessed performing chemical bonding tests. The fs-laser machining process has shown great potential for the mass production of microfluidic devices. The developed process has enabled for a reduction of up to 90% in the fabrication times of the insert compared to micromilling. The parts exhibited very smooth surfaces, with roughness values (Sa) of 64.6 nm for the metallic insert and 71.8 nm and 72.9 nm for the COC E-140 and 8007S-04 replicas, respectively. The dimensional tolerance and the surface quality need to be improved to be competitive with the finishes achieved with precision micromilling. Nonetheless, there is still room for improvement considering the significant reduction in the production times through new laser processing strategies. Full article

(This article belongs to the Special Issue Advances in Polymers: From Fabrication Technologies to Applications in Biotechnology and Biomedicine)

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33 pages, 3407 KiB

Open AccessReview

Advances in Toughening Modification Methods for Epoxy Resins: A Comprehensive Review

by Jiawei Zhang, Zhen Zhang, Ran Huang and Lianjiang Tan

Polymers 2025, 17(9), 1288; https://doi.org/10.3390/polym17091288 - 7 May 2025

Viewed by 315

Abstract

This work provides a comprehensive review of the recent advancements in the toughening modification methods for epoxy resins. The study explores a variety of approaches, including the incorporation of liquid rubbers, core–shell rubber particles, thermoplastic resins, hyperbranched polymers, and the nanoparticle toughening method, [...] Read more.

This work provides a comprehensive review of the recent advancements in the toughening modification methods for epoxy resins. The study explores a variety of approaches, including the incorporation of liquid rubbers, core–shell rubber particles, thermoplastic resins, hyperbranched polymers, and the nanoparticle toughening method, each of which contributes to improving the mechanical properties and fracture toughness of epoxy resins. Special attention is given to the mechanisms underlying these toughening methods, such as reaction-induced phase separation, crack pinning, and energy dissipation through particle deformation. The paper also examines the synergistic effects achieved by combining different toughening agents, such as phenoxy thermoplastic rubber and core–shell rubber particles, which significantly enhance the critical fracture energy and impact strength of epoxy composites. Additionally, the challenges associated with each method, such as the potential reduction in mechanical properties and the influence of phase separation on material performance, are discussed. Through a detailed analysis of experimental studies, this paper highlights the effectiveness of various toughening strategies and suggests future research directions aimed at further optimizing epoxy resin toughening techniques for diverse industrial applications. Emerging computational modeling and machine learning applications in epoxy resin development are also systematically reviewed to highlight their potential in advancing predictive design frameworks. Full article

(This article belongs to the Special Issue Polymer Nanocomposites with Improved Mechanical, Thermal, Electrical and Barrier Properties)

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35 pages, 4072 KiB

Open AccessReview

Advances in Digital Light Processing (DLP) Bioprinting: A Review of Biomaterials and Its Applications, Innovations, Challenges, and Future Perspectives

by Cem Alparslan and Şenol Bayraktar

Polymers 2025, 17(9), 1287; https://doi.org/10.3390/polym17091287 - 7 May 2025

Viewed by 256

Abstract

Digital light processing (DLP) technology stands out as a groundbreaking method in the field of biomedical engineering that enables the production of highly precise structures using photopolymerizable materials. Smart materials such as shape memory polymers, hydrogels, and nanocomposites are used as ideal materials [...] Read more.

Digital light processing (DLP) technology stands out as a groundbreaking method in the field of biomedical engineering that enables the production of highly precise structures using photopolymerizable materials. Smart materials such as shape memory polymers, hydrogels, and nanocomposites are used as ideal materials for personalized medicine applications thanks to their properties such as superior mechanical strength, biocompatibility, and sensitivity to environmental stimuli in DLP technology. The integration of these materials with DLP enables the production of functional and complex structures, especially in areas such as bone and soft tissue engineering, drug delivery, and biosensor production. However, limited material diversity, scalability problems in production processes, and technical difficulties in optimizing bioprinting parameters are among the main obstacles in this field. This study systematically examines the role of smart biomaterials in DLP-based bioprinting processes. It addresses the innovative applications of these materials in tissue engineering and regenerative medicine. It also comprehensively evaluates its contributions to biomedical applications and discusses future research areas to overcome current limitations. Full article

(This article belongs to the Section Polymer Processing and Engineering)

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15 pages, 3552 KiB

Open AccessArticle

The Size Effect on the Phase Transition and Dielectric Properties of Poly(vinylidene Fluoride) Ferroelectric Polymers

by Xiaofang Zhao, Min Yu and Xining Zhang

Polymers 2025, 17(9), 1286; https://doi.org/10.3390/polym17091286 - 7 May 2025

Viewed by 152

Abstract

Multi-scale characterization techniques have been employed to analyze the size effect of microstructure on the phase transition behavior and dielectric properties of poly(vinylidene fluoride) (PVDF) films. The results show that oriented amorphous fraction layers are prone to form in the vicinity of the [...] Read more.

Multi-scale characterization techniques have been employed to analyze the size effect of microstructure on the phase transition behavior and dielectric properties of poly(vinylidene fluoride) (PVDF) films. The results show that oriented amorphous fraction layers are prone to form in the vicinity of the grain boundaries of nano-grained films, while the interfacial polarization and electrostriction effect play a major role. Polar nano-regions are prone to form in micro-grained films, and the maximum fraction of polar crystalline phase and maximal dielectric constant can be achieved due to the balance between the intrinsic effect and extrinsic effect of the material. On the contrary, the extrinsic effect corresponding to interfacial charges greatly influences the phase transition behavior between beta and alpha phases for coarse-grained PVDF films, while the dielectric properties are mainly influenced by the intrinsic electrostatic field and van der Waal interaction of the material. Hence, the dielectric behavior of nano-grained films can be adjusted by the copolymerization technique, that of micro-grained films can be adjusted by both the copolymerization technique and the controlling of microstructure morphology, and that of coarse-grained films can be adjusted by the doping technique. Full article

(This article belongs to the Section Polymer Physics and Theory)

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12 pages, 1151 KiB

Open AccessArticle

Photocurable Crosslinker from Bio-Based Non-Isocyanate Poly(hydroxyurethane) for Biocompatible Hydrogels

by Kathleen Hennig, Gabriele Vacun, Sibylle Thude and Wolfdietrich Meyer

Polymers 2025, 17(9), 1285; https://doi.org/10.3390/polym17091285 - 7 May 2025

Viewed by 175

Abstract

This study explores the synthesis of photocurable non-isocyanate polyhydroxyethylurethanes (BPHUs) derived from renewable sources, designed for biomedical applications and the development towards advanced light curing processes. The following two pathways were developed: an aliphatic route using 1,4-butanediol-derived cyclic carbonates and an aromatic route [...] Read more.

This study explores the synthesis of photocurable non-isocyanate polyhydroxyethylurethanes (BPHUs) derived from renewable sources, designed for biomedical applications and the development towards advanced light curing processes. The following two pathways were developed: an aliphatic route using 1,4-butanediol-derived cyclic carbonates and an aromatic route with resorcinol-based carbonates. Ring-opening polymerization with dodecanediamine produced BPHU intermediates, which were methacrylated to form photoreactive derivatives (aliphatic MAs and aromatic MAs). Comprehensive characterization, including NMR, GPC, and FTIR, confirmed the successful synthesis. The UV curing of these methacrylated compounds yielded hydrogels with swelling properties. Aliphatic BPHUs achieved a gel content of 91.3% and a swelling of 1057%, demonstrating the flexibility and UV stability suitable for adaptable biomedical applications. Conversely, aromatic BPHUs displayed a gel content of 78.1% and a swelling of 3304%, indicating higher rigidity, which is advantageous for load-bearing uses. Cytotoxicity assessments adhering to the DIN EN ISO 10993-5 standard demonstrated non-cytotoxicity, with an >80% cell viability for both variants. This research underscores the potential of green chemistry in crafting biocompatible, versatile BPHUs, paving the way for eco-friendly materials in implantable medical devices. Full article

(This article belongs to the Section Biobased and Biodegradable Polymers)

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28 pages, 4904 KiB

Open AccessReview

Nondestructive Testing of Externally Bonded FRP Concrete Structures: A Comprehensive Review

by Eyad Alsuhaibani

Polymers 2025, 17(9), 1284; https://doi.org/10.3390/polym17091284 - 7 May 2025

Viewed by 199

Abstract

The growing application of Fiber-Reinforced Polymer (FRP) composites in rehabilitating deteriorating concrete infrastructure underscores the need for reliable, cost-effective, and automated nondestructive testing (NDT) methods. This review provides a comprehensive analysis of existing and emerging NDT techniques used to assess externally bonded FRP [...] Read more.

The growing application of Fiber-Reinforced Polymer (FRP) composites in rehabilitating deteriorating concrete infrastructure underscores the need for reliable, cost-effective, and automated nondestructive testing (NDT) methods. This review provides a comprehensive analysis of existing and emerging NDT techniques used to assess externally bonded FRP (EB-FRP) systems, emphasizing their accuracy, limitations, and practicality. Various NDT methods, including Ground-Penetrating Radar (GPR), Phased Array Ultrasonic Testing (PAUT), Infrared Thermography (IRT), Acoustic Emission (AE), and Impact–Echo (IE), are critically evaluated in terms of their effectiveness in detecting debonding, voids, delaminations, and other defects. Recent technological advancements, particularly the integration of artificial intelligence (AI) and machine learning (ML) in NDT applications, have significantly improved defect characterization, automated inspections, and real-time data analysis. This review highlights AI-driven NDT approaches such as automated crack detection, hybrid NDT frameworks, and drone-assisted thermographic inspections, which enhance accuracy and efficiency in large-scale infrastructure assessments. Additionally, economic considerations and cost–performance trade-offs are analyzed, addressing the feasibility of different NDT methods in real-world FRP-strengthened structures. Finally, the review identifies key research gaps, including the need for standardization in FRP-NDT applications, AI-enhanced defect quantification, and hybrid inspection techniques. By consolidating state-of-the-art research and emerging innovations, this paper serves as a valuable resource for engineers, researchers, and practitioners involved in the assessment, monitoring, and maintenance of FRP-strengthened concrete structures. Full article

(This article belongs to the Section Polymer Processing and Engineering)

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20 pages, 1869 KiB

Open AccessArticle

Production of β-Glucans from Rhizopus oryzae M10A1 by Optimizing Culture Conditions Using Liquid Potato Starch Waste

by Miguel Anchundia, Gualberto León-Revelo, Stalin Santacruz and Freddy Torres

Polymers 2025, 17(9), 1283; https://doi.org/10.3390/polym17091283 - 7 May 2025

Viewed by 176

Abstract

β-glucans from filamentous fungi are important for human health. There is limited research on polysaccharides from filamentous fungi, and no reports have been published regarding the optimization of culture media to produce β-glucans from Rhizopus oryzae using liquid waste from potato starch processing. [...] Read more.

β-glucans from filamentous fungi are important for human health. There is limited research on polysaccharides from filamentous fungi, and no reports have been published regarding the optimization of culture media to produce β-glucans from Rhizopus oryzae using liquid waste from potato starch processing. In this regard, the fermentation conditions to produce β-glucans from Rhizopus oryzae M10A1 were optimized using the one variable at a time (OVAT) and response surface methodology (RSM). The β-glucans were chemically characterized by determining moisture, nitrogen, protein, fat, ash, and total carbohydrates. The color, molecular weight, β-glucan content, monosaccharide composition, and structural and conformational characteristics were assessed by colorimetry, gel permeation chromatography, high-performance liquid chromatography, and Fourier transform infrared spectroscopy, respectively. The microbial indicators, mesophilic aerobes, molds, yeasts, and Escherichia coli were quantified following ISO standard protocols. Optimization indicated that supplementation with 0.8% (w/v) glucose and ammonium sulfate enhanced heteroglycan production (3254.56 mg/100 g of biomass). The β-glucans exhibited high purity, a light brown color, a molecular weight of 450 kDa, and a composition predominantly consisting of glucose and galactose. These findings suggest that β-glucans from Rhizopus oryzae M10A1 could be used for food and health applications. Full article

(This article belongs to the Special Issue Carbohydrate Polymers: Synthesis, Preparation, Structural Characteristics and Applications)

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21 pages, 7391 KiB

Open AccessArticle

Recycling of Plastic Waste in the Construction Industry

by Nancy Sakr and Mohamed AbouZeid

Polymers 2025, 17(9), 1282; https://doi.org/10.3390/polym17091282 - 7 May 2025

Viewed by 214

Abstract

This study underscores the importance of sustainable practices by exploring the utilization of recycled plastic within the global construction industry. Plastic recycling has emerged as a crucial strategy that aligns with environmental, social, and economic sustainability indicators. Currently, substantial volumes of plastic waste [...] Read more.

This study underscores the importance of sustainable practices by exploring the utilization of recycled plastic within the global construction industry. Plastic recycling has emerged as a crucial strategy that aligns with environmental, social, and economic sustainability indicators. Currently, substantial volumes of plastic waste are either deposited in landfills or incinerated, neglecting the potential to harness its embodied energy and the energy consumed for producing virgin materials. A key advantage of plastic lies in its promising mechanical properties. Concrete mix design is fundamental to a wide range of construction applications, including brick walls, reinforced concrete slabs, and concrete pavements. Despite the adoption of recycled plastic in construction materials in various countries, its widespread implementation remains limited. This is primarily due to the scarcity of experimental research in this area and the absence of a robust waste management system. This research specifically investigates the reuse of two common types of plastic waste: polyethylene terephthalate (PET) and high-density polyethylene (HDPE) to mitigate plastic waste accumulation in landfills and enhance the performance of construction materials. The study investigates the use of recycled HDPE and PET as a replacement for coarse aggregates in concrete pavement mixtures. While recycled PET is more prevalent in concrete applications, recycled HDPE has demonstrated exceptional efficiency and durability. The recycling method used in this research is the mechanical recycling method due to its superior effectiveness in comparison with other methodologies. This research assesses the performance of recycled PET and HDPE in concrete pavement, aiming to diminish non-renewable energy consumption by 15–20%, curtail the carbon footprint by 15–30%, and decrease plastic waste in landfills by 20–30% compared to conventional concrete. Full article

(This article belongs to the Special Issue Recycling of Plastic and Rubber Wastes, 2nd Edition)

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13 pages, 3353 KiB

Open AccessArticle

Rational Designing of NiO Nanoparticles Anchored with PEG-WO₃ for Enhanced Water Oxidation Performance

by Mrunal Bhosale, Pritam J. Morankar, Rutuja U. Amate and Chan-Wook Jeon

Polymers 2025, 17(9), 1281; https://doi.org/10.3390/polym17091281 - 7 May 2025

Viewed by 173

Abstract

The electrochemical water splitting method is widely regarded as an efficient and sustainable approach for producing high-purity hydrogen in an environmentally friendly manner. Cost-effective and efficient electrocatalysts are essential for augmenting the electrocatalytic water oxidation reaction. Herein, the PEG-WO₃-NiO electrocatalyst is [...] Read more.

The electrochemical water splitting method is widely regarded as an efficient and sustainable approach for producing high-purity hydrogen in an environmentally friendly manner. Cost-effective and efficient electrocatalysts are essential for augmenting the electrocatalytic water oxidation reaction. Herein, the PEG-WO₃-NiO electrocatalyst is acknowledged for attaining efficient oxygen evolution reaction (OER) performances in alkaline conditions. The NiO nanoparticles anchored themselves to the PEG-WO₃‘s surface and produced an effective interfacial contact between the electrocatalyst materials. Among various compositions, the optimized ratio of the PEG-WO₃-NiO electrocatalyst exhibits a low overpotential of 349.7 mV at a current density of 10 mA cm⁻² and a Tafel slope of 71.22 mV dec⁻¹ for the OER in 1 M KOH. Additionally, the electrocatalyst demonstrates excellent stability, maintaining its performance even after 5000 cyclic voltammetry (CV) cycles and chronopotentiometry analysis. Given its durability and high electrochemically active surface area, the PEG-WO₃-NiO electrocatalyst contributes to the advancement of cost-effective and scalable solutions for water oxidation applications. Full article

(This article belongs to the Special Issue Graphene-Based Polymer Composites: Synthesis and Applications)

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11 pages, 3377 KiB

Open AccessArticle

A Poly(Acrylamide-co-Acrylic Acid)-Encapsulated Nitrification Inhibitor with Good Soil-Loosening, Phosphorous-Solubilizing, and Nitrogen Fixation Abilities and High-Temperature Resistance

by Hui Gao, Yuli Fu, Tianyu Wang, Meijia Liu, Jianzhen Mao and Feng Xu

Polymers 2025, 17(9), 1280; https://doi.org/10.3390/polym17091280 - 7 May 2025

Viewed by 124

Abstract

3,4-dimethylpyrazole (DMPZ), when used as a nitrification inhibitor, exhibits volatility, poor thermal stability, high production costs, and limited functionality restricted to nitrogen fixation. To address these limitations and introduce novel phosphorus-solubilizing and soil-loosening abilities, herein, a poly (acrylamide-co-acrylic acid)-encapsulated NI (P(AA- [...] Read more.

3,4-dimethylpyrazole (DMPZ), when used as a nitrification inhibitor, exhibits volatility, poor thermal stability, high production costs, and limited functionality restricted to nitrogen fixation. To address these limitations and introduce novel phosphorus-solubilizing and soil-loosening abilities, herein, a poly (acrylamide-co-acrylic acid)-encapsulated NI (P(AA-co-AM)-e-NI) is synthesized by incorporating linear P(AM-co-AA) macromolecular structures into NI systems. The P(AA-co-AM)-e-NI demonstrates an obvious phase transition from a glassy state to a rubbery state, with a glass transition temperature of ~150 °C. Only 5 wt% of the weight loss occurs at 220 °C, meeting the temperature requirements of the high-tower melt granulation process (≥165 °C). The DMPZ content in P(AA-co-AM)-e-NI is 1.067 wt%, representing a 120% increase compared to our previous products (0.484 wt%). P(AA-co-AM)-e-NI can effectively reduce the abundance of ammonia-oxidizing bacteria and prolong the duration during which nitrogen fertilizers exist in the form of ammonium nitrogen. It can also cooperatively enhance the conversion of insoluble phosphorus into soluble phosphorus in the presence of ammonium nitrogen (NH₄⁺-N). In addition, upon adding P(AA-co-AM)-e-NI into soils, soil bulk density and hardness decrease by 9.2% and 10.5%, respectively, and soil permeability increases by 10.5%, showing that it has a good soil-loosening ability and capacity to regulate the soil environment. Full article

(This article belongs to the Section Polymer Applications)

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14 pages, 546 KiB

Open AccessArticle

The Effect of Sterilization Methods on the Mechanical Properties of 3D-Printed and Conventional PMMA Materials for Denture Bases of Immediate Obturators

by Anna Cybulska, Katarzyna Mańka-Malara, Michał Krasowski, Jerzy Sokołowski, Jakub Zwoliński, Andrzej Rafalski and Jolanta Kostrzewa-Janicka

Polymers 2025, 17(9), 1279; https://doi.org/10.3390/polym17091279 - 7 May 2025

Viewed by 156

Abstract

The use of 3D printing in the fabrication of immediate prosthetic restorations requires the possibility of sterilization. This study aimed to evaluate the effects of different sterilization methods on the parameters of 3D-printing materials for dental prosthesis plates compared to conventional acrylic material. [...] Read more.

The use of 3D printing in the fabrication of immediate prosthetic restorations requires the possibility of sterilization. This study aimed to evaluate the effects of different sterilization methods on the parameters of 3D-printing materials for dental prosthesis plates compared to conventional acrylic material. Forty-four samples were prepared for each tested material: Denture 3D+ (NextDent, The Netherlands), Denturetec (Saremco, Switzerland), Optiprint Laviva (Dentona, Germany), and Rapid Simplified (Vertex Dental, Netherlands). The impact strength of the samples was tested in a HIT 5.5P instrument (Zwick Roell, Germany) after three sterilization methods (pressurized steam, ethylene oxide, and radiation) and without sterilization as a control group. Significantly higher energy and impact strength were recorded for the conventional acrylic material. For Nextdent material, the recommended method of sterilization in terms of impaction is autoclave or ethylene oxide sterilization, Saremco—ethylene oxide sterilization, and Denton—ethylene oxide or radiation sterilization. Conventional acrylic material has a higher impact strength than 3D-printed material, which may encourage the selection of this material for restorations requiring higher fracture strength. The possibility of sterilizing the Nextdent 3D-printed material in the autoclave without worsening its durability makes it a recommended choice for digital clinical practice. Full article

(This article belongs to the Special Issue Functional Polymeric Materials for Dental and Oral and Maxillofacial Surgery Applications)

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2 pages, 2529 KiB

Open AccessCorrection

Correction: Ijaz et al. Biofunctional Hyaluronic Acid/κ-Carrageenan Injectable Hydrogels for Improved Drug Delivery and Wound Healing. Polymers 2022, 14, 376

by Uzma Ijaz, Muhammad Sohail, Muhammad Usman Minhas, Shahzeb Khan, Zahid Hussain, Mohsin Kazi, Syed Ahmed Shah, Arshad Mahmood and Mohammed Maniruzzaman

Polymers 2025, 17(9), 1278; https://doi.org/10.3390/polym17091278 - 7 May 2025

Viewed by 138

Abstract

In the original publication [...] Full article

(This article belongs to the Special Issue Functional Polymer Materials for Cell-Based Tissue Regeneration)

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17 pages, 4896 KiB

Open AccessArticle

Urea–Formaldehyde Strengthened by Polyvinyl Alcohol: Impact on Mulch Film Properties and Cucumber Cultivation

by Tingting Shen, Yongjie Ma and Xueyan Zhang

Polymers 2025, 17(9), 1277; https://doi.org/10.3390/polym17091277 - 7 May 2025

Viewed by 150

Abstract

To address the problem of environmental pollution caused by the extensive use of low-density polyethylene (LDPE) mulch film, this study developed a novel sprayable mulch using natural fibers and biodegradable polymers. Urea–formaldehyde resin (UF), strengthened with polyvinyl alcohol (PVA), was used as a [...] Read more.

To address the problem of environmental pollution caused by the extensive use of low-density polyethylene (LDPE) mulch film, this study developed a novel sprayable mulch using natural fibers and biodegradable polymers. Urea–formaldehyde resin (UF), strengthened with polyvinyl alcohol (PVA), was used as a modifier to induce beneficial physicochemical structural changes in PVA-modified urea–formaldehyde (PUF) resins. Characterization of these resins was conducted using Fourier transformation infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Preparation of the biodegradable mulch was conducted using Xuan paper waste residue (XP) as an enhancer, with PUF as the auxiliary agent. The resulting film (PUF-XP) was examined for differences in thickness, morphological characterization, and rate of weight loss, and the effects of different covering films on cucumber growth, root development, soil temperature, and weed control were evaluated. Characterization reveals that when the PVA content was 4% (W4UF), the film had the lowest free formaldehyde content (0.26%) and highest elongation at break (5.70%). In addition, W4UF could easily undergo thermal degradation at 278.4 °C and possessed a close-knit, three-dimensional structural network. W4UF was then mixed with paper powder and water in various proportions to produce three mulch films (BioT1, BioT2, and BioT3) that demonstrated excellent water retention and heat preservation and inhibited weed growth by 68.8–96.8%. Compared to no mulching (NM), BioT1 increased both the specific root length and root density, as well as improved the plant height, stem diameter, and total biomass of the cucumbers by 43.5%, 34.1%, and 33.9%, respectively. Therefore, a mass ratio of paper powder, water, and W4UF of 1:30:2 produced a biodegradable mulch film that could be used as an alternative to LDPE, mitigating the environmental pollution rendered by synthetic plastic mulch films and offering the potential for a sustainable agricultural application. Full article

(This article belongs to the Special Issue (Bio)Polymer-Based Composite Materials: Advancements and New Trends in Biomedical Engineering and Research)

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20 pages, 5821 KiB

Open AccessArticle

Synthesis and Characterization of Fully Bio-Based Butylene Succinate Oligomers with Varying Molecular Weights for Sustainable Food Packaging Applications

by Carmen Olivas-Alonso, Yaiza Flores, Antxon Martínez de Ilarduya, Amparo Chiralt and Sergio Torres-Giner

Polymers 2025, 17(9), 1276; https://doi.org/10.3390/polym17091276 - 7 May 2025

Viewed by 186

Abstract

The development of bio-based and biodegradable materials is critical for reducing environmental impact and addressing global challenges associated with the extensive use of plastics in packaging applications. In this study, linear oligomers of butylene succinate (OBS) with three different molecular weights were synthesized [...] Read more.

The development of bio-based and biodegradable materials is critical for reducing environmental impact and addressing global challenges associated with the extensive use of plastics in packaging applications. In this study, linear oligomers of butylene succinate (OBS) with three different molecular weights were synthesized using succinic acid (SA) and 1,4-butanediol (BDO), both monomers derived from biomass. The synthesized fully bio-based OBS samples were characterized in terms of their molecular structure, degree of polymerization, crystallinity, and thermal properties, showcasing their potential as additives for biopolymers in food packaging. Oligomers with weight-average molecular weight (M_w) values of 2050 g·mol⁻¹ (OBS-L), 16,150 g·mol⁻¹ (OBS-M), and 33,147 g·mol⁻¹ (OBS-H), and Ð values in the 1.7–1.8 range were successfully synthesized. The results showed that the thermal degradation stability of OBS slightly increased, while the crystallinity decreased with increasing molecular weight. Furthermore, the analysis of the evolution of the lattice parameters suggested that oligomers with shorter chains favored crystal organization, resulting in a crystal unit cell with denser packing. Full article

(This article belongs to the Section Biobased and Biodegradable Polymers)

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14 pages, 4181 KiB

Open AccessArticle

Behavioral Study of Elastomeric O-Rings Built into Coaxial Sealing Systems

by Andrea Deaconescu and Tudor Deaconescu

Polymers 2025, 17(9), 1275; https://doi.org/10.3390/polym17091275 - 7 May 2025

Viewed by 116

Abstract

Coaxial sealing systems are increasingly used in the construction of hydraulic cylinders. In addition to the seal that ensures the actual packing of the entire system, the O-ring plays an important role in the functioning of the hydraulic subassembly. In order to understand [...] Read more.

Coaxial sealing systems are increasingly used in the construction of hydraulic cylinders. In addition to the seal that ensures the actual packing of the entire system, the O-ring plays an important role in the functioning of the hydraulic subassembly. In order to understand the sealing phenomenon of coaxial systems, a physical and mathematical model of the contact between the O-ring and its contacting surfaces is required. Within this context, this paper presents a calculation method of the pressures generated in the contact areas of the O-ring with its adjacent surfaces, as well as of the widths of the contact areas. The input quantities for these calculations were certain material characteristics (hardness, elasticity modulus, and Poisson’s coefficient) of the sealed-off fluid pressure and the specific radial deformation, which is a characteristic that describes the mounting of the O-ring in its groove. This article concludes with recommendations for the mounting of the O-ring and the required characteristics of the used materials. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Romania (2024,2025))

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11 pages, 1029 KiB

Open AccessArticle

A Straightforward Methodology for the Quantification of Long Chain Branches in Polyethylene by ¹³C NMR Spectroscopy

by Francesco Zaccaria, Andrea Pucciarelli, Roberta Cipullo and Vincenzo Busico

Polymers 2025, 17(9), 1274; https://doi.org/10.3390/polym17091274 - 7 May 2025

Viewed by 220

Abstract

Formation of long chain branches (LCB) in polyethylene (PE), via incorporation of in situ generated vinyl macromonomers, is known to affect material properties dramatically, making their detection and quantification of primary importance. ¹³C NMR spectroscopy is the archetypal technique for the analysis [...] Read more.

Formation of long chain branches (LCB) in polyethylene (PE), via incorporation of in situ generated vinyl macromonomers, is known to affect material properties dramatically, making their detection and quantification of primary importance. ¹³C NMR spectroscopy is the archetypal technique for the analysis of polymer microstructure, yet it suffers from major limitations in the analysis of LCB in polyethylene, primarily in terms of resolution. Herein, we propose a simple and effective methodology for detecting and quantifying LCB based on the analysis of C atoms in β-position with respect to the branching point. By analyzing model ethylene/α-olefin copolymers bearing methyl, ethyl, butyl, hexyl or tetradecyl chain branches, we show how the C_β resonances can be used to discriminate between shorter or longer branches. Importantly, the proposed method allows the most critical discrimination between hexyl-type branches and LCB, with an up to three-fold detection enhancement with respect to previously proposed procedures based on the analysis of the methine carbons. The proposed approach is then tested on a representative industrial sample of HDPE, proving that it is suitable to detect very small amounts of LCB. Full article

(This article belongs to the Section Polymer Chemistry)

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15 pages, 3677 KiB

Open AccessArticle

Unveiling Thermal Degradation and Fire Behavior of 110 kV Ultra-High-Voltage Flame-Retardant Cable Sheath After Thermal Aging

by Yaqiang Jiang, Wei He, Xinke Huo, Xuelian Lu, Kaiyuan Li and Fei Xiao

Polymers 2025, 17(9), 1273; https://doi.org/10.3390/polym17091273 - 6 May 2025

Viewed by 196

Abstract

To evaluate the fire safety of 110 kV ultra-high-voltage flame-retardant polyvinyl chloride (PVC) cables in the service process, the effects of thermal aging on the pyrolysis and combustion behavior of the cable sheaths were studied using thermogravimetric (TG), limiting oxygen index (LOI), UL-94 [...] Read more.

To evaluate the fire safety of 110 kV ultra-high-voltage flame-retardant polyvinyl chloride (PVC) cables in the service process, the effects of thermal aging on the pyrolysis and combustion behavior of the cable sheaths were studied using thermogravimetric (TG), limiting oxygen index (LOI), UL-94 vertical burning, cone calorimeter, open flame, and muffle furnace tests. The results showed that thermal aging causes a slight decrease in the LOI value of the cable sheath (28.3% vs. 28.5%), but it also passed the UL-94 V-0 test. The butane torch test showed that the cable sheath was more easily ignited after aging; however, a better char layer was formed in the later stage of burning, which led to a longer failure time. Interestingly, the aging treatment prolonged the ignition time of the cable sheaths and reduced the peak heat release rate (pHRR) and total heat release (THR) by 17.5% and 24.4%, respectively, in the cone calorimeter test, indicating that aging resulted in a reduction in the fire hazard of the cable sheaths. Moreover, aging mechanisms were proposed based on the composition and structural evolution of the cable sheaths. In summary, this work comprehensively evaluated the fire hazard of 110 kV ultra-high-voltage cables and provided theoretical support for the formulation improvement, durability enhancement, and fire protection design of cable sheath materials. Full article

(This article belongs to the Special Issue Advances in Fire-Safe Polymer Materials)

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16 pages, 5820 KiB

Open AccessArticle

Mechanical, Antibacterial, and Physico-Chemical Properties of Three Different Polymer-Based Direct Restorative Materials: An In Vitro Study

by Chloé Laporte, Rim Bourgi, Hamdi Jmal, Teissir Ben Ammar, Sandy Hazko, Frédéric Addiego, Salvatore Sauro, Youssef Haïkel and Naji Kharouf

Polymers 2025, 17(9), 1272; https://doi.org/10.3390/polym17091272 - 6 May 2025

Viewed by 383

Abstract

A novel resin-based bulk-fill restorative material (ST; Stela SDI, Bayswater, Victoria, Australia) has been recently introduced as a self-curing alternative to traditional light-cured composites. Promoted for its unlimited depth of cure, enhanced aesthetics, and unique primer composition, it aims to address challenges associated [...] Read more.

A novel resin-based bulk-fill restorative material (ST; Stela SDI, Bayswater, Victoria, Australia) has been recently introduced as a self-curing alternative to traditional light-cured composites. Promoted for its unlimited depth of cure, enhanced aesthetics, and unique primer composition, it aims to address challenges associated with amalgam and light-curing composites. Thus, the aim of this in vitro study was to investigate the performance of the new self-curing polymer-based restorative material, ST, compared to two conventional light-cured composites for direct restoration. The study evaluated compressive strength with and without aging, antibacterial activity, mineral deposition in contact with Phosphate-Buffered Saline (PBS) and artificial saliva, porosity, and wettability of ST (Tetric EvoCeram (TE; Ivoclar Vivadent, Schaan, Liechtenstein) and Clearfil Majesty ES-2 (CM; Kuraray Noritake Dental, Tokyo, Japan)). The data was statistically analyzed (α = 0.05) through one-way and two-way analysis of variance (ANOVA). ST demonstrated significantly higher compressive strength than TE and CM at baseline and after aging (p < 0.001), while aging significantly reduced compressive strength across all materials (p < 0.001). Fracture mode analysis revealed brittle fractures for TE and CM, whereas ST fractured in multiple smaller fragments. CM showed the highest void volume and diameter, significantly differing from ST and TE (p < 0.001). Scanning electron microscopy (SEM) analysis revealed cubical-like crystalline formations on ST’s surface after 28 days of immersion in PBS and saliva, indicating some level of bioactivity, whereas no changes were observed for TE and CM. Wettability testing showed ST had the lowest contact angle (12.24° ± 2.1°) compared to TE (62.78° ± 4.68°) and CM (64.64° ± 3.72°) (p < 0.001). Antibacterial activity testing displayed a significant decrease in bacterial growth for CM compared to ST (p = 0.001) and TE (p = 0.002); however, ST and TE showed no significant differences (p = 0.950). To conclude, ST Automix demonstrated promising results across several key parameters, making it a potential candidate for long-lasting restorative applications. Future studies should explore its long-term clinical performance and investigate formulations that enhance its antibacterial properties. Moreover, the bond strength of these materials to dentin and the cytotoxicity should be evaluated. Full article

(This article belongs to the Special Issue Physicochemical Properties of Polymer Composites)

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25 pages, 8618 KiB

Open AccessArticle

MWCNT Localization and Electrical Percolation in Thin Films of Semifluorinated PMMA Block Copolymers

by Ulrike Staudinger, Andreas Janke, Frank Simon, Lothar Jakisch, Eva Bittrich, Petr Formanek, Lukas Mielke, Hendrik Schlicke, Qiong Li, Kathrin Eckstein and Doris Pospiech

Polymers 2025, 17(9), 1271; https://doi.org/10.3390/polym17091271 - 6 May 2025

Viewed by 186

Abstract

Diblock copolymers (BCP) consisting of poly(methyl methacrylate) (PMMA) and poly(1H,1H,2H,2H-perfluorodecyl methacrylate) (PsfMA) blocks are employed as templates for controlled dispersion and localization of multi-walled carbon nanotubes (MWCNT). Short MWCNT are modified with perfluoroalkyl groups to increase the compatibility between MWCNT and the semifluorinated [...] Read more.

Diblock copolymers (BCP) consisting of poly(methyl methacrylate) (PMMA) and poly(1H,1H,2H,2H-perfluorodecyl methacrylate) (PsfMA) blocks are employed as templates for controlled dispersion and localization of multi-walled carbon nanotubes (MWCNT). Short MWCNT are modified with perfluoroalkyl groups to increase the compatibility between MWCNT and the semifluorinated (PsfMA) phase and to promote a defined arrangement of MWCNT in the BCP morphology. Thin BCP and BCP/MWCNT composite films are prepared by dip-coating using tetrahydrofuran as solvent with dispersed MWCNT. Atomic force microscopy, scanning and transmission electron microscopy reveal a strong tendency of the BCP to form micelle-like domains consisting of a PMMA shell and a semifluorinated PsfMA core, embedded in a soft phase, containing also semifluorinated blocks. MWCNT preferentially localized in the embedding phase outside the micelles. Perfluoroalkyl-modification leads to significant improvement in the dispersion of MWCNT, both in the polymer solution and the resulting nanocomposite film due to increased interaction of MWCNT with the semifluorinated side chains in the soft phase outside the micelle domains. As a result, reliable electrical conductivity is observed in contrast to films with non-modified MWCNT. Thus, well-dispersed, modified MWCNT provide a defined electrical conduction path at the micrometer level, which is interesting for applications in electronics and vapor sensing. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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19 pages, 7736 KiB

Open AccessArticle

An Analysis of Foams Produced from Recycled Polyolefins and Low-Cost Foaming Agents: Benchmarking Using Pore Size, Distribution, Shear Effects, and Thermal Properties

by Krishnamurthy Prasad, Fareed Tamaddoni Jahromi, Shammi Sultana Nisha, John Stehle, Emad Gad and Mostafa Nikzad

Polymers 2025, 17(9), 1270; https://doi.org/10.3390/polym17091270 - 6 May 2025

Viewed by 175

Abstract

Foamed specimens were fabricated from virgin and recycled polyethylenes (linear low-density polyethylene, LLDPE, and low-density polyethylene, LDPE) using low-cost citric acid and sodium bicarbonate foaming agents. The foaming agents chosen showed decomposition behaviour either without phase change (sodium bicarbonate, NaB) or liquefaction followed [...] Read more.

Foamed specimens were fabricated from virgin and recycled polyethylenes (linear low-density polyethylene, LLDPE, and low-density polyethylene, LDPE) using low-cost citric acid and sodium bicarbonate foaming agents. The foaming agents chosen showed decomposition behaviour either without phase change (sodium bicarbonate, NaB) or liquefaction followed by decomposition (citric acid, CA). The manufactured polyethylene foams were then benchmarked against a polyurethane foam. Two types of mixing were used prior to foaming, viz., solid-state pulverisation or high-shear internal mixing, and the effect of mixing on properties critical for foam viability were analysed. These properties included density, pore size, shape and distribution, crystallinity, and porosity. It was found that the virgin LLDPE and recycled LDPE showed similar trends in terms of narrow pore size distribution and reduced crystallinity, while the recycled LLDPE tended towards more pore coalescence. This difference in behaviour was attributed to the more mixed phase nature of the recycled LLDPE as opposed to the majorly single-phase virgin LLDPE and recycled LDPE. Lowered densities obtained for the NaB foaming compared to CA can be speculated to be because of the ionic and simple NaB decomposition as opposed to the complex radical pathway for the CA decomposition. Full article

(This article belongs to the Special Issue Polymer Manufacturing Processes)

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15 pages, 2796 KiB

Open AccessArticle

Incorporation of Ag-ZnO Nanoparticles into PVDF Membrane Formulation to Enhance Dye Retention, Permeability, and Antibacterial Properties

by Baha Chamam, Roua Ben Dassi, Jraba Abderraouf, Jean Pierre Mericq, Catherine Faur, Ismail Trabelsi, Lassaad El Mir and Marc Heran

Polymers 2025, 17(9), 1269; https://doi.org/10.3390/polym17091269 - 6 May 2025

Viewed by 268

Abstract

Ultrafiltration is essential for wastewater treatment, but it faces challenges such as selectivity, control, and fouling reduction. Incorporating nanoparticles into membranes enhances retention, boosts permeability, and limits fouling, improving overall performance. This study explores the properties of PVDF/Ag-ZnO composite membranes, highlighting the influence [...] Read more.

Ultrafiltration is essential for wastewater treatment, but it faces challenges such as selectivity, control, and fouling reduction. Incorporating nanoparticles into membranes enhances retention, boosts permeability, and limits fouling, improving overall performance. This study explores the properties of PVDF/Ag-ZnO composite membranes, highlighting the influence of silver-doped zinc oxide nanoparticles on membrane structure, performance, and antimicrobial effect. The non-solvent-induced phase separation (NIPS) method successfully led to the preparation of composite membranes; this method used different doses of silver-doped zinc oxide (Ag-ZnO) nanoparticles with Poly(vinylidene fluoride) (PVDF). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and water contact angle measurements were used to validate the influence of nanoparticles on the composite membrane (PVDF/Ag-ZnO) structure. Conversely, morphology (porosity, surface rigorosity), hydrophilicity, and permeability were analyzed through contact angle, image analysis, and flux measurement. In addition, the membranes were tested for antimicrobial activity against E. coli. Membrane performance shows that the incorporation of 20% w/w Ag-ZnO resulted in improved water permeability, which was about 2.73 times higher than that of a pure PVDF membrane (192.2 L·m⁻²·h⁻¹·bar⁻¹). The membrane porosity showed a linear increase with the number of NPs. The resultant asymmetric membrane was altered to increase the number of pores on the top surface by 61% and the cross-sectional pore surface by 663%. Furthermore, a high antibacterial activity of Ag-ZnO 20% was shown. Full article

(This article belongs to the Special Issue Innovative Polymers and Technology for Membrane Fabrication)

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20 pages, 3343 KiB

Open AccessArticle

Unraveling the Reactivity of SiO₂-Supported Nickel Catalyst in Ethylene Copolymerization with Polar Monomers: A Theoretical Study

by Daniela E. Ortega and Diego Cortés-Arriagada

Polymers 2025, 17(9), 1268; https://doi.org/10.3390/polym17091268 - 6 May 2025

Viewed by 226

Abstract

Understanding the catalytic behavior of heterogeneous systems for the copolymerization of ethylene with polar monomers is essential for developing advanced functional polyolefins. In this study, we conducted a quantum chemical investigation of the SiO₂-supported Ni–allyl–α-imine ketone catalyst (Ni-OH@SiO₂) to [...] Read more.

Understanding the catalytic behavior of heterogeneous systems for the copolymerization of ethylene with polar monomers is essential for developing advanced functional polyolefins. In this study, we conducted a quantum chemical investigation of the SiO₂-supported Ni–allyl–α-imine ketone catalyst (Ni-OH@SiO₂) to uncover the factors governing monomer insertion, selectivity, and reactivity. Using DFT calculations and energy decomposition analysis (ALMO-EDA), we evaluated the coordination and insertion of six industrially relevant polar monomers, comparing their behavior to ethylene homopolymerization. Our results show that special polar monomers (SPMs) with aliphatic spacers, such as vinyltrimethoxysilane (vTMS) and 5-hexenyl acetate (AMA), exhibit favorable insertion profiles due to enhanced electrostatic and orbital interactions with minimal steric hindrance. In contrast, fundamental polar monomers (FPMs), including methyl acrylate (MA) and vinyl chloride (vCl), show higher activation barriers and increased Pauli repulsion due to strong electron-withdrawing effects and conjugation with the vinyl group. AMA displayed the lowest activation barrier (7.4 kcal/mol) and highest insertion thermodynamic stability (−17.6 kcal/mol). These findings provide molecular-level insight into insertion mechanisms and comonomer selectivity in Ni–allyl catalysts supported on silica, extending experimental understanding. This work establishes key structure–reactivity relationships and offers design principles for developing efficient Ni-based heterogeneous catalysts for polar monomer copolymerization. Full article

(This article belongs to the Special Issue Status and Progress of Soluble Polymers II)

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31 pages, 7533 KiB

Open AccessArticle

Quantitative DSC Assessment of the Polymorph-Specific Crystallinity of Poly(Lactic Acid) and the Impact of a Self-Assembling Nucleating Agent and PEG Plasticizer

by Maarten Colaers, Wim Thielemans and Bart Goderis

Polymers 2025, 17(9), 1267; https://doi.org/10.3390/polym17091267 - 6 May 2025

Viewed by 163

Abstract

This study examines the temperature-resolved, polymorph-specific crystallinity of poly(lactic acid), PLA, during cooling and heating at 10 °C/min, with a focus on the effects of N, N-bis(benzoyl) hexanedioic acid dihydrazide (BHAD, commercially known as TMC306) as nucleating agent and PEG 1000 as plasticizer. [...] Read more.

This study examines the temperature-resolved, polymorph-specific crystallinity of poly(lactic acid), PLA, during cooling and heating at 10 °C/min, with a focus on the effects of N, N-bis(benzoyl) hexanedioic acid dihydrazide (BHAD, commercially known as TMC306) as nucleating agent and PEG 1000 as plasticizer. A semicrystalline (PLA-1) and amorphous (PLA-2) PLA grade were investigated. The study emphasizes the importance of using temperature-dependent, polymorph-specific transition enthalpies to accurately calculate crystallinities from Differential Scanning Calorimetry (DSC). Polymorphism is independently confirmed using Wide Angle X-ray Diffraction (WAXD). Pure PLA-1 reached an α′ crystallinity of 2% during cooling, which increased to 38% through cold crystallization upon heating. At BHAD concentrations of at least 0.4%, α crystallites formed instead of α′, reaching a maximum crystallinity of 38% during cooling. The addition of 10 wt% PEG to PLA-1 facilitated primary α crystallization during cooling, followed by secondary intraspherulitic α′ crystallization upon heating, resulting ultimately in a crystallinity of 34%. Adding 1 wt% BHAD into PLA-1 with 10 wt% PEG shifted the crystallization temperature upward by 40 °C and enhanced the α crystallinity to 44%, highlighting the synergistic effect of PEG and BHAD on crystallization. Full article

(This article belongs to the Special Issue Advances in the Thermal Characterization of Polymers and Plastic Waste)

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18 pages, 6782 KiB

Open AccessFeature PaperArticle

Preparation, Reaction Kinetics, and Properties of Polyester Foams Using Water Produced by the Reaction as a Foaming Agent

by Fabian Weitenhagen and Oliver Weichold

Polymers 2025, 17(9), 1266; https://doi.org/10.3390/polym17091266 - 6 May 2025

Viewed by 261

Abstract

This study explores sustainable foamed polyester materials derived from natural or bio-based building blocks, including succinic, glutaric, and adipic acids, combined with trimethylolpropane and pentaerythritol. By precisely tuning the ratio of functional groups, the resulting polymers contain minimal free functionalities, leading to lower [...] Read more.

This study explores sustainable foamed polyester materials derived from natural or bio-based building blocks, including succinic, glutaric, and adipic acids, combined with trimethylolpropane and pentaerythritol. By precisely tuning the ratio of functional groups, the resulting polymers contain minimal free functionalities, leading to lower hygroscopicity and enhanced stability. The reaction is monitored by tracking the mass loss associated with water formation, the primary condensation by-product, which reveals a first-order kinetic behaviour. Infrared spectroscopy indicates that foaming occurs in a narrow time window, while esterification begins earlier and continues afterwards. Thermogravimetric analysis confirms thermal stability up to ~400 °C, with complete decomposition at 500 °C and no residue. Scanning electron microscopy images of test specimens with varying densities reveal dense, microporosity-free cell walls in both materials, indicating a homogeneous polymer matrix that contributes to the overall stabilisation of the foam structure. In flammability tests, the foams resist ignition during two 10 s methane flame exposures and, under prolonged flame, burn 40 times more slowly than conventional foams. These results demonstrate a modular system for creating bio-based foams with tunable properties—from soft and elastic to rigid—suitable for diverse applications. The materials offer a sustainable alternative to petrochemical foams while retaining excellent mechanical and thermal properties. Full article

(This article belongs to the Special Issue Designing Polymers for Emerging Applications)

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16 pages, 4455 KiB

Open AccessArticle

Saccharide Alterations in Spruce Wood Due to Thermal and Accelerated Aging Processes

by František Kačík, Tereza Jurczyková, Magdaléna Bálintová, Elena Kmeťová, Eva Výbohová and Danica Kačíková

Polymers 2025, 17(9), 1265; https://doi.org/10.3390/polym17091265 - 6 May 2025

Viewed by 319

Abstract

This work is devoted to the changes in polysaccharides in thermally treated wood after its accelerated aging with the aim of its optimal utilization after its original use has ended. Spruce wood samples were treated by the Thermowood process at temperatures of 160 [...] Read more.

This work is devoted to the changes in polysaccharides in thermally treated wood after its accelerated aging with the aim of its optimal utilization after its original use has ended. Spruce wood samples were treated by the Thermowood process at temperatures of 160 °C, 180 °C, and 210 °C and subjected to accelerated aging in wet mode. The influence of treatment temperature and accelerated aging was monitored by wet chemistry, high-performance liquid chromatography (HPLC), X-ray diffraction (XRD), size exclusion chromatography (SEC), and Fourier-transform infrared spectroscopy (FTIR). During thermal treatment, hemicelluloses are mainly degraded. At the temperature of 210 °C, aromatic compounds formed as degradation products of lignin and hemicelluloses bind to cellulose fibers and increase cellulose yield. Preferential decomposition of the amorphous portion of cellulose leads to an increase in its crystallinity, while higher temperatures cause degradation of the crystal lattice. The degree of polymerization in both cellulose and hemicelluloses decreases due to the cleavage of glycosidic bonds. Accelerated aging does not significantly affect the changes in polysaccharides. The results obtained can be used in the processing of cellulose and hemicelluloses from thermally modified wood at the end of its life cycle in various industrial fields. Full article

(This article belongs to the Special Issue Life Cycle and Utilization of Lignocellulosic Materials)

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13 pages, 2931 KiB

Open AccessArticle

Effect of Injection Molding Parameters on the Tensile Strength of Short-Carbon-Fiber-Reinforced Nylon 6

by Runtian Zhao, Xiaodong Li, Zhihui Wang, Ting Wu and Jianguo Liang

Polymers 2025, 17(9), 1264; https://doi.org/10.3390/polym17091264 - 6 May 2025

Viewed by 279

Abstract

SCF/PA6 composites have gained extensive industrial applications due to their superior processability and moldability, with long-fiber pellet injection molding being the predominant manufacturing technique. However, systematic investigations into injection molding parameter optimization and its mechanistic impacts on tensile strength remain scarce. This study [...] Read more.

SCF/PA6 composites have gained extensive industrial applications due to their superior processability and moldability, with long-fiber pellet injection molding being the predominant manufacturing technique. However, systematic investigations into injection molding parameter optimization and its mechanistic impacts on tensile strength remain scarce. This study employed the Taguchi method to investigate the effects of four critical process parameters—injection pressure, melt temperature, mold temperature, and injection time—on the tensile strength of short-carbon-fiber-reinforced nylon 6 (SCF/PA6), while elucidating their underlying mechanisms. The optimal parameter combination within the experimental range was determined to be an injection pressure of 100 bar, a melt temperature of 280 °C, a mold temperature of 100 °C, and an injection time of 2 s. Under these optimized conditions, the tensile strength reached 184.33 MPa, representing an 8.05% enhancement over baseline values. Mechanistic analysis revealed that melt temperature and injection time (essentially reflecting injection velocity) primarily govern fiber orientation distribution. Notably, melt temperature additionally regulates molecular chain orientation in the amorphous matrix regions. Injection pressure predominantly influences process-induced defect formation and material densification. Mold temperature exhibits a negligible impact on tensile strength. Full article

(This article belongs to the Section Polymer Processing and Engineering)

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21 pages, 1192 KiB

Open AccessReview

Advancing Organ-on-a-Chip Systems: The Role of Scaffold Materials and Coatings in Engineering Cell Microenvironment

by Guido Andrés Ramírez-González, Chiara Consumi-Tubito, Ernesto Vargas-Méndez and Carolina Centeno-Cerdas

Polymers 2025, 17(9), 1263; https://doi.org/10.3390/polym17091263 - 6 May 2025

Viewed by 434

Abstract

For organ-on-a-chip (OoC) engineering, the use of biocompatible coatings and materials is not only recommended but essential. Extracellular matrix (ECM) components are commonly used as coatings due to their effects on cell orientation, protein expression, differentiation, and adhesion. Among the most frequently used [...] Read more.

For organ-on-a-chip (OoC) engineering, the use of biocompatible coatings and materials is not only recommended but essential. Extracellular matrix (ECM) components are commonly used as coatings due to their effects on cell orientation, protein expression, differentiation, and adhesion. Among the most frequently used coatings are collagen, fibronectin, and Matrigel, according to the specific cell type and intended OoC application. Additionally, materials such as polydimethylsiloxane (PDMS), thermoplastics, chitosan, and alginate serve as scaffolding components due to their biomechanical properties and biocompatibility. Here, we discuss some of the most employed coating techniques, including SAMs, dip coating, spin coating, microcontact printing, and 3D bioprinting, each offering advantages and drawbacks. Current challenges comprise enhancing biocompatibility, exploring novel materials, and improving scalability and reproducibility. Full article

(This article belongs to the Special Issue Biocompatible and Biodegradable Polymer Materials)

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20 pages, 6542 KiB

Open AccessArticle

Diclofenac-Loaded Orodispersible Nanofibers Prepared by Double-Needle Electrospinning

by Luca Éva Uhljar, Tekla Jáger, Csongor Hajdu, Anett Motzwickler-Németh, Orsolya Jójárt-Laczkovich, Martin Cseh, Katalin Burian and Rita Ambrus

Polymers 2025, 17(9), 1262; https://doi.org/10.3390/polym17091262 - 6 May 2025

Viewed by 291

Abstract

The main aim of this study was to develop a diclofenac-loaded, orodispersible formulation prepared by double-needle electrospinning. For the use of two needles, one above the other, a new needle holder was designed and 3D printed. During the optimization of the drug-free PVP [...] Read more.

The main aim of this study was to develop a diclofenac-loaded, orodispersible formulation prepared by double-needle electrospinning. For the use of two needles, one above the other, a new needle holder was designed and 3D printed. During the optimization of the drug-free PVP carrier, the effect of the polymer concentration on the morphology and average fiber diameter was investigated. Electrospinning was possible for solutions with a PVP concentration between 7.5 and 15 w/w%. Too low viscosity led to smooth-surfaced nanoparticles, since electrospraying occurred. The optimal material properties and process parameters were used to prepare drug-loaded nanofibers. The morphology, crystallinity, chemical interactions, encapsulation efficiency, drug distribution, in vitro disintegration, in vitro dissolution, cytocompatibility, and 6-month stability were tested. According to the results, the electrospun formulation was an amorphous solid dispersion with excellent encapsulation efficiency. The drug distribution was homogeneous within the nanofiber matrix. The disintegration was completed in about 5 s in artificial saliva and about 41 s on an artificial tongue. The dissolution in artificial saliva was complete within 10 min. Overall, a promising formulation was developed with rapid disintegration, immediate drug release, and good stability. Additionally, a new in vitro dissolution method (“AS-to-FaSSGF”) was developed to obtain a bigger picture of drug dissolution throughout the gastrointestinal tract. Full article

(This article belongs to the Special Issue Multifunctional Application of Electrospun Fiber)

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18 pages, 1064 KiB

Open AccessArticle

Post-Curing Effects on the Tensile Properties of Hybrid Fiber-Reinforced Polymers: Experimental and Numerical Insights

by Mohammed Zaini, Oumayma Hamlaoui, Jalal Chafiq, Mohamed Ait El Fqih, Mohamed Idiri, Said Aqil, Mohamed Karim Hajji, Alperen Bal, Hakan Tozan, Marta Harnicárová and Jan Valicek

Polymers 2025, 17(9), 1261; https://doi.org/10.3390/polym17091261 - 6 May 2025

Viewed by 304

Abstract

This study investigates the effects of post-curing temperatures on the tensile properties of hybrid basalt-jute-glass-carbon fiber-reinforced polymers (FRPs). Composite specimens were post-cured at 60 °C and 100 °C for 60 min, and their tensile behavior was assessed using a servo-hydraulic testing machine. Numerical [...] Read more.

This study investigates the effects of post-curing temperatures on the tensile properties of hybrid basalt-jute-glass-carbon fiber-reinforced polymers (FRPs). Composite specimens were post-cured at 60 °C and 100 °C for 60 min, and their tensile behavior was assessed using a servo-hydraulic testing machine. Numerical simulations using the Abaqus software V6.14 were also conducted to compare experimental and computational results. The findings indicate that post-curing heat treatment enhances ductility due to increased polymer cross-linking, but excessive heat treatment at 100 °C negatively impacts elongation at fracture. The results revealed that specimens post-cured at 60 °C exhibited the optimal balance between strength and ductility, with increased elongation and moderate tensile strength. However, at 100 °C, while tensile strength improved in some cases, a significant decrease in elasticity and an increased risk of brittleness were observed, suggesting that extreme heat treatment may degrade polymer integrity. Natural fiber composites, particularly jute-based samples, outperformed synthetic composites in terms of elongation and overall mechanical stability. The numerical simulations provided further insights but showed discrepancies with experimental results, mainly due to fiber property variations and fabric waviness, underscoring the challenges of accurately modeling woven composites. The study highlights the importance of controlled post-curing temperatures in optimizing the mechanical performance of FRP composites, with 60 °C identified as the most effective condition for achieving a favorable balance between tensile strength, flexibility, and material durability. These findings offer valuable insights for material scientists and engineers working on the development of high-performance composite materials for structural and industrial applications. Full article

(This article belongs to the Special Issue Advanced Fiber-Reinforced Polymer Composites: Design, Manufacturing, Characterization, and Application)

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21 pages, 4982 KiB

Open AccessArticle

New Explosive-Circulation Technology of Tire Recycling for the Production of Crumb Rubber with Modified Surface

by Vyacheslav M. Misin, Alexander A. Nabok, Alexander A. Zakharov, Alexey V. Krivandin, Natalia I. Krikunova, Vladimir A. Volkov, Mikhail V. Voronkov, Sergey I. Pozin, Alexey K. Buryak, Alexander E. Tarasov, Alexander V. Naumkin and Sergey S. Nikulin

Polymers 2025, 17(9), 1260; https://doi.org/10.3390/polym17091260 - 5 May 2025

Viewed by 388

Abstract

The article reports on the development of a fundamentally new, effective technology for recycling waste tires using the explosive-circulation technology method, which was implemented in industry at a working factory. The construction of an explosion-circulation reactor, in which tires are destroyed under the [...] Read more.

The article reports on the development of a fundamentally new, effective technology for recycling waste tires using the explosive-circulation technology method, which was implemented in industry at a working factory. The construction of an explosion-circulation reactor, in which tires are destroyed under the influence of an explosion, is described. The main technological stages of the reactor operation include the formation of a tire package with a height of about 2.4 m and a mass of up to 1000 kg; cooling the package by air turbo-cooling machine to a temperature of minus 70–80 °C; placing the package into the reactor; initiating the explosive charge; and removing the tire shedding products with a subsequent granulometric classification of the resulting rubber crumb. The resulting rubber crumb has good wettability, which eliminates the need for an additional technological stage of activating the crumb surface. This made it possible to successfully use the obtained rubber crumb to improve the characteristics of road construction bitumen, the hardness of which at −16 °C decreased from 217 to 161 MPa. Using atomic force microscopy (AFM), gas chromatography, mass spectrometry, GPC, and XPS, it was established that the good wettability of the crumbs is explained by the formation of molecules with polar groups (C-O, C=O, C(O)O, C-S, C-SO_x, Zn-S, O-Si(O)-O) on the crumb surface as a result of the explosion. Full article

(This article belongs to the Section Circular and Green Sustainable Polymer Science)

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